1. Field of the Invention
The present invention relates to a mass analyzer using an ion trap and an operation method thereof.
2. Description of the Related Art
MS/MS analysis is effective for identification of molecular species because structure information of precursor ions is obtained from patterns of fragment ions. In addition, an influence of noise resulting from contaminants can be averted and therefore, MS/MS analysis is widely used also for quantitative analyses. How such analyses have been carried out will be described below.
A method of carrying out an MS/MS analysis using an ion trap is described, for example, in U.S. Pat. No. 7,078,685. Sample ions are introduced into the ion trap to be trapped. Next, all ions of the trapped ions excluding specific precursor ions are removed. Subsequently, precursor ions remaining in the trap are caused to be dissociated by, for example, collisional dissociation with an inert gas. Lastly, fragment ions generated by dissociation of precursor ions are selectively ejected based on masses.
A method of carrying out an MS/MS analysis using a mass analyzer constituted by inserting a collisional dissociation part between two quadrupole mass filters is described, for example, in Biomedical mass spectrometry, Vol. 8, p 397 (1981). Only specific precursor ions of ions introduced into the mass analyzer are allowed to selectively pass through the first-stage quadrupole mass filter to remove all other ions. Next, the precursor ions are caused to be dissociated by the collisional dissociation part by means of, for example, collisional dissociation with an inert gas. The second-stage quadrupole mass filter is used to carry out a mass analysis of fragment ions generated in the collisional dissociation part.
A method of carrying out an MS/MS analysis using a mass analyzer constituted by inserting a collisional dissociation part between a quadrupole mass filter and a time-of-flight mass analyzer is described, for example, in Rapid Communications in Mass Spectrometry, Vol. 10, pp. 889-896 (1996). Only specific precursor ions of ions introduced into the mass analyzer are allowed to selectively pass through the quadrupole mass filter to remove all other ions. Next, precursor ions are caused to be dissociated by the collisional dissociation part by means of, for example, collisional dissociation with an inert gas. The time-of-flight mass analyzer is used to carry out a mass analysis of fragment ions generated in the collisional dissociation part. Though, with this constitution, the mass analysis of fragment ions can be carried out with higher resolution compared with a constitution in which a quadrupole mass filter is used for mass analysis of fragment ions, utilization efficiency of ions will decline.
A method of carrying out an MS/MS analysis using a mass analyzer constituted by inserting a collisional dissociation part between two time-of-flight mass analyzers is described, for example, in U.S. Pat. No. 5,464,985. The first-stage time-of-flight mass analyzer is used to carry out an MS/MS analysis of ions introduced into the mass analyzer and only specific precursor ions are introduced into the collisional dissociation part to remove all other ions. Next, precursor ions are caused to be dissociated by the collisional dissociation part by means of, for example, collisional dissociation with an inert gas. Lastly, the second-stage time-of-flight mass analyzer is used to carry out a mass analysis of fragment ions generated in the collisional dissociation part. With this constitution, precursor ions can be selected with higher resolution compared with a constitution in which a quadrupole mass filter is used for selection of precursor ions.
A method of carrying out a precursor scan or neutral loss scan, which are a type of the MS/MS analysis, using a mass analyzer constituted by inserting a collisional dissociation part between an ion trap and a time-of-flight mass analyzer or between an ion trap and a quadrupole mass filter is described, for example, in U.S. Pat. No. 6,504,148. Ions introduced into the mass analyzer are once trapped in the ion trap. The trapped ions are successively ejected before being introduced into the collisional dissociation part. Next, precursor ions are caused to be dissociated by the collisional dissociation part by means of, for example, collisional dissociation with an inert gas. Subsequently, the time-of-flight mass analyzer or the quadrupole mass filter is used to carry out a mass analysis of fragment ions generated in the collisional dissociation part. With this constitution, utilization efficiency of ions by the precursor ion scan or neutral loss scan will be higher compared with a case in which precursor ions are selected by a time-of-flight mass analyzer or a quadrupole mass filter.